title: In vitro and in vivo evaluations of a hydrophilic 64Cu-bis(thiosemicarbazonato)-glucose conjugate for hypoxia imaging.
abstract: A water-soluble glucose conjugate of the hypoxia tracer 64Cu-diacetyl-bis(N4-methylthiosemicarbazone) (64Cu-ATSM) was synthesized and radiolabeled (64Cu-ATSE/A-G). Here we report our initial biological experiments with 64Cu-ATSE/A-G and compare the results with those obtained for 64Cu-ATSM and 18F-FDG.
  
  
  METHODS
  The uptake of 64Cu-ATSE/A-G and 64Cu-ATSM into HeLa cells in vitro was investigated at a range of dissolved oxygen concentrations representing normoxia, hypoxia, and anoxia. Small-animal PET with 64Cu-ATSE/A-G was performed in male BDIX rats implanted with P22 syngeneic carcinosarcomas. Images of 64Cu-ATSM and 18F-FDG were obtained in the same model for comparison.
  
  
  RESULTS
  64CuATSE/A-G showed oxygen concentration-dependent uptake in vitro and, under anoxic conditions, showed slightly lower levels of cellular uptake than 64Cu-ATSM; uptake levels under hypoxic conditions were also lower. Whereas the normoxic uptake of 64Cu-ATSM increased linearly over time, 64Cu-ATSE/A-G uptake remained at low levels over the entire time course. In the PET study, 64CuATSE/A-G showed good tumor uptake and a biodistribution pattern substantially different from that of each of the controls. In marked contrast to the findings for 64Cu-ATSM, renal clearance and accumulation in the bladder were observed. 64Cu-ATSE/A-G did not display the characteristic brain and heart uptake of 18F-FDG.
  
  
  CONCLUSIONS
  The in vitro cell uptake studies demonstrated that 64Cu-ATSE/A-G retained hypoxia selectivity and had improved characteristics when compared with 64Cu-ATSM. The in vivo PET results indicated a difference in the excretion pathways, with a shift from primarily hepatointestinal for 64Cu-ATSM to partially renal with 64Cu-ATSE/A-G. This finding is consistent with the hydrophilic nature of the glucose conjugate. A comparison with 18F-FDG PET results revealed that 64Cu-ATSE/A-G was not a surrogate for glucose metabolism. We have demonstrated that our method for the modification of Cu-bis(thiosemicarbazonato) complexes allows their biodistribution to be modified without negating their hypoxia selectivity or tumor uptake properties.
authors.affiliation: Siemens Oxford Molecular Imaging Laboratory, Inorganic Chemistry Laboratory, University of Oxford, Oxford, United Kingdom.
authors.forename: Simon R
authors.initials: SR
authors.lastname: Bayly
authors.forename: Robert C
authors.initials: RC
authors.lastname: King
authors.forename: Davina J
authors.initials: DJ
authors.lastname: Honess
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Barnard
authors.forename: Helen M
authors.initials: HM
authors.lastname: Betts
authors.forename: Jason P
authors.initials: JP
authors.lastname: Holland
authors.forename: Rebekka
authors.initials: R
authors.lastname: Hueting
authors.forename: Paul D
authors.initials: PD
authors.lastname: Bonnitcha
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Dilworth
authors.forename: Franklin I
authors.initials: FI
authors.lastname: Aigbirhio
authors.forename: Martin
authors.initials: M
authors.lastname: Christlieb
mesh_terms: D000818:Animals; D002296:Carcinosarcoma / Q000000981:diagnostic imaging; D003301:Copper Radioisotopes / Q000737:chemistry*; D019788:Fluorodeoxyglucose F18; D005947:Glucose / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D000860:Hypoxia / Q000000981:diagnostic imaging* / Q000378:metabolism; D008297:Male; D010100:Oxygen / Q000378:metabolism; D049268:Positron-Emission Tomography; D051381:Rats; D013882:Thiosemicarbazones / Q000097:blood / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D003301:Copper Radioisotopes; D013882:Thiosemicarbazones; D019788:Fluorodeoxyglucose F18; D005947:Glucose; D010100:Oxygen